Conventional methods used for hollow forming can be divided into two categories, one of which applies air-blowing method to expand the inner space of material in the mould so that a hollow object may be formed. With this method, the forming speed is low and the thickness of product wall can not be well controlled. Another method of forming is then developed which may rotate the mould in a single direction to speed the production, however, defects such as bubbles often exist in the surface of products which reversely affects the quality of products.
Therefore, it is tried by the applicant to develop the present invention of a hollow forming machine which may rotate moulds thereon in both horizontal and vertical directions and can eliminate the above-mentioned drawbacks existing in prior art.